1.3 Bonding Flashcards
Metalic bond
Attraction between positive metal ions and delocalised electrons
Ionic bond
Electrostatic attraction between oppositely charged ions
Which elements do not form ions?
Boron
Carbon (usually)
Silicon (usually)
What ions does tin form?
Sn⁴⁺ (most stable) and Sn²⁺
What ions does lead form?
Mostly Pb²⁺ but some Pb⁴⁺
Covalent bond
A shared pair of electrons
What is a lone pair?
A pair of electrons which are not bonded
What are non-octet molecules?
Molecules where the central atom does not have a noble gas electron arrangement
Coordinate bond
A covalent bond in which both electrons of the shared pair come from the same atom
How does a lone pair effect the bond angle?
Reduces angle by 2.5 degrees
Electronegativity
The power of an atom to attract the pair of electrons in a covalent bond
Most electronegative atom
Fluorine
Why does electronegativity increase across a period?
The number of protons (nuclear charge) increases
Why does electronegativity decrease down a group?
Atomic radius increases as the number of shells increases
Why don’t the noble gasses have electronegativity values?
They do not usually form covalent bonds
Three types of intermolecular force
- van der Waals’s forces
- Permanent dipole-dipole forces
- Hydrogen bonds
Electron deficient
Where the central atom of a non-octet molecule has fewer electrons than the noble gas configuration
Expanded octet
Where the central atom of a non-octet molecule has more electrons than the noble gas configuration
Shape:
2 bond pairs
0 lone pairs
Linear
(180°)
Shape and angle:
3 bond pairs
0 lone pairs
Trigonal planar
(120°)
Shape and angle:
4 bond pairs
0 lone pairs
Tetrahedral
(109.5°)
Shape and angle:
5 bond pairs
0 lone pairs
Trigonal bipyramidal
(90° and 120°)
Shape and angle:
6 bond pairs
0 lone pairs
Octohedral
(90°)
Shape and angle:
2 bond pairs
1 lone pairs
V-shaped
(117.5°)
Shape and angle:
3 bond pairs
1 lone pairs
Trigonal pyramidal
(107°)
Shape and angle:
2 bond pairs
2 lone pairs
V-shaped
(104.5°)
Shape and angle:
3 bond pairs
2 lone pairs
Trigonal planar
(120°)
Shape and angle:
4 bond pairs
2 lone pairs
Square planar
(90°)
van der Waals’ forces
- Movement of electrons unbalances charge distributions creating an instantiations dipole.
- This induces a dipole in the neighbouring molecules
Effect of Mr on strength of van der Waals’ forces
Larger molecules have more electrons so there are larger induced dipoles, so forces are stronger.
Permanent dipole-dipole forces
- Positive and negative ends of neighbouring molecules are attracted to each other
- Occur in addition to van der Waals’ forces
Hydrogen bonding
- Forms between positive H atom and the lone pair of the neighbouring molecule
- Occur in addition to van der Waals’ forces
Which atoms can hydrogen bond with for hydrogen bonds to form between molecules?
Nitrogen
Oxygen
Fluorine
(Most electronegative atoms)
Properties of substances with hydrogen bonding
- Higher boiling points than other substances with similar Mrs
- Usually dissolve in water (forms hydrogen bonds with water)
What is needed for a substance to dissolve?
Attraction between solute and solvent molecules
What do ionic and polar substances dissolve in?
Polar solvents
What do non-polar substances dissolve in?
Non-polar solvents
Why are metals malleable and ductile?
Layers of ions in the giant metallic lattice can slide over each other without disrupting the metallic bond
Why are ionic substances brittle?
If layers in a giant ionic lattice slide over each other, they cause like charges to line up, the repulsion causes the structure to break down.
